Apparatus and method for detecting cells or particles in a fluid container

ABSTRACT

A apparatus for detecting cells or particles in a fluid container includes a dispenser configured to dispense at least one cell or at least one particle into a defined sub-volume of a fluid with which the fluid container is at least partially filled, and a detection apparatus configured to, in a time-coordinated manner with dispensing the at least one cell or the at least one particle by the dispenser, perform a detection in the defined sub-volume and/or in one or several sub-volumes underneath the defined sub-volume in order to sense the at least one cell or the at least one particle when entering the fluid or immediately after entering the fluid.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from German Patent Application No.102016211038.1, which was filed on Jun. 21, 2016, which is incorporatedherein in its entirety by this reference thereto.

BACKGROUND OF THE INVENTION

The present invention concerns apparatuses and methods for detectingcells or particles dispensed by a dispenser into a defined sub-volume ofa fluid located in a fluid container.

After inserting cells or particles into a fluid container, sensing ifthe cell or the particle is actually located in the fluid container isgenerally often performed. For example, monoclonal antibodies and otherproteins, which are subsequently called products, are prepared by meansof so-called monoclonal cell lines. These are populations of cellsoriginating from a single cell. This ensures to the best extent that allcells of the population comprise approximately the same genotype and,thus, generate a product which is as equal as possible.

In order to generate a monoclonal cell line, cells are individuallytransferred into so-called microtiter plates and multiply there in acontrolled manner until the desired population size is reached.Depositing single cells in the microtiter plates occurs by free-jetprinting methods or by pipetting single cells into the single bowls orcavities of the microtiter plate, which are herein after referred to as“wells”. These wells represent containers. When manufacturingtherapeutic products from cell cultures, it has to be demonstrated forregulatory reasons that indeed only one cell was located in the well atthe beginning of the process. It is important for the well bottom to besufficiently large, i.e., significantly larger than a cell, in order toallow the population to grow to the useful size. Ultimately, from aseries of a few hundreds to thousands of such clone populations, the onethat produces the desired product in the most stable manner and in thegreatest quantity is transferred to manufacturing.

Methods for sensing cells in fluid containers, for example, the wells ofa microtiter plate, are known from the conventional technology.

In “Assurance of monoclonality in one round of cloning through cellsorting for single cell deposition coupled with high resolution cellimaging”, 2015, American Institute of Chemical Engineers, Biotechnol.Prog., vol. 00, No. 00, http://doi.org/10.1002/btpr.2145, K. Evans et aldescribe a process for producing monoclonal cell lines. Cells aretransferred into the well of a microtiter plate by means of a so-calledFACS apparatus (FACS=fluorescent activated cell sorting). After that,the same is centrifuged in order to transport the cells to the bottom.Successively, the entire well bottom is examined under the microscope,typically by means of a so-called imager, and single cells are searchedfor therein, which is effected by the user. In this case, it isextremely difficult to recognize a single cell in the large observationvolume.

Flow cytometry represents a known method for analyzing cells passing anelectric voltage or a light ray. For example, U.S. Pat. No. 3,380,584 Adescribes a method for separating particles in which a printing methodcomprising a continuous jet is employed, which has the disadvantage ofdrops being continuously generated without being able to interrupt thedrop stream in a controlled manner. In selectively sorting cells orparticles by means of this technique, the drops are therefore depositedat different positions according to content. This occurs by anelectrostatic deflection during flight. The higher the number ofpositions and the involved deposition accuracy (e.g., in 96 or 384 wellplates), the more difficult and technically complex the process. From EP0 421 406 A2, apparatuses and methods for separating particles areknown, in which a thermal printing head is used in order to dispenseparticles. The particles are arbitrarily arranged in the reservoir andare optically analyzed after ejection during flight. The above-describedmethods allow for depositing cells individually but cannot achieve anefficiency of 100 percent. Therefore, the microtiter plates have to beexamined under the microscope afterwards by means of so-called imagers.

From U.S. Pat. No. 7,310,147 B2, EP 1 686 368 A2, U.S. Pat. No.8,417,011 B2 and U.S. Pat. No. 8,795,981 B2, apparatuses and methods forsensing cells and particles in microtiter plates are known.

U.S. Pat. No. 7,646,482 B2 describes a method for automatically findingthe right focal plane in order to, e.g., examine cells at a well bottomunder a microscope. In the course of this, the method detects patternsin the sensor signal, while the microscope focuses through the bottom ofthe plate.

U.S. Pat. No. 8,383,042 B2 describes an imager comprising a vacuumholder. The vacuum holder sucks in the microtiter plate in order tomaintain the bottom of the microtiter plate in a plane manner and, inthis way, provides a lower variance of the distance of the well bottomto the objective.

From WO 2011/154042 A1, apparatuses and methods for dispensing a cell ora particle in a free-flying droplet are known

The inventors have realized that current dispensing methods forindividually depositing may detect and deposit cells with highefficiency, while not being 100% reliable.

SUMMARY

According to an embodiment, an apparatus for detecting cells orparticles in a fluid container may have: a dispenser configured todispense at least one cell or at least one particle into a definedsub-volume of a fluid with which the fluid container is at leastpartially filled; a detection apparatus configured to, in atime-coordinated manner with dispensing the at least one cell or the atleast one particle by the dispenser, perform a detection in the definedsub-volume and/or in one or several sub-volumes underneath the definedsub-volume in order to sense the at least one cell or the at least oneparticle when entering the fluid or immediately after entering thefluid.

According to another embodiment, a method for detecting cells orparticles in a fluid container may have the steps of: dispensing atleast one cell or at least one particle into a defined sub-volume of afluid with which a fluid container is at least partially filled;performing, in a time-coordinated manner with dispensing the at leastone cell or the at least one particle, a detection in the definedsub-volume and/or in one or several sub-volumes underneath the definedsub-volume in order to sense the at least one cell or the at least oneparticle when entering the fluid or immediately after entering thefluid.

Embodiments of the invention provide an apparatus for detecting cells orparticles in a fluid container, comprising:

a dispenser configured to dispense at least one cell or at least oneparticle into a defined sub-volume of a fluid with which the fluidcontainer is at least partially filled;

a detection apparatus configured to, in a time-coordinated manner withdispensing the at least one cell or the at least one particle by thedispenser, perform a detection in the defined sub-volume and/or in oneor several sub-volumes underneath the defined sub-volume in order tosense the at least one cell or the at least one particle when enteringthe fluid or immediately after entering the fluid.

Embodiments of the invention provide a method for detecting cells orparticles in a fluid container, comprising:

dispensing at least one cell or at least one particle into a definedsub-volume of a fluid with which a fluid container is at least partiallyfilled; and

performing, in a time-coordinated manner with dispensing the at leastone cell or the at least one particle, a detection in the definedsub-volume and/or in one or several sub-volumes underneath the definedsub-volume in order to sense the at least one cell or the at least oneparticle when entering the fluid or immediately after entering thefluid.

In embodiments of the invention, the object, i.e., the cell or theparticle, such as the single cell or the single particle, is neitherdetected in the dispenser nor in a free-flying drop in which the objectis dispensed. Thus, in embodiments, the detection does not occur duringtransport, e.g., into the well of a microtiter plate. Rather, the cellor the particle is sensed when entering the fluid or immediately afterentering the fluid which at least partially fills the fluid container inwhich the cell or the particle is to be sensed. Thus, embodiments allowfor a reliable verification that the cell or the particle has ended upin the fluid container and is actually located in the fluid container.In embodiments, the dispenser dispenses a free-flying drop in which theobject, i.e., the cell or the particle, is encapsulated so that areliable verification that the drop has actually landed in the fluidcontainer, e.g., a well of a microtiter plate, is possible in suchembodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will be detailed subsequentlyreferring to the appended drawings, in which:

FIG. 1 shows a schematic illustration of an apparatus for detectingcells or particles in a fluid container;

FIG. 2 shows a schematic illustration of an apparatus comprising anoptical sensor;

FIG. 3 shows a schematic illustration of a fluid container;

FIG. 4 shows a flowchart of an embodiment of a method for detectingcells or particles in a fluid container;

FIG. 5 shows a comparison of an embodiment of a method for detectingcells or particles in a fluid container described herein with a knownmethod; and

FIG. 6 shows schematic illustrations of fluid containers for explainingproblems occurring in known methods.

DETAILED DESCRIPTION OF THE INVENTION

Before the embodiments are described successively, it is to be notedthat the invention is not restricted by these special embodiments, butby the wording of the claims.

Furthermore, at first, some of the terms used herein are described. Adispenser is understood to be an apparatus configured for dispensingcells or particles. Examples of dispensers may be drop generatorsconfigured for dispensing liquid quantities in the form of free-flyingdrops. A drop-on-demand printing technology is understood to be aprinting technology enabling selectively generating single drops from anozzle at a chosen point in time. In contrast, a continuous-jet printingtechnology is understood to be a printing technology in which a thincontinuous liquid jet is dispensed from a nozzle in a pressure-drivenmanner. By applying a high-frequency oscillation at the nozzle, afterdischarge, the jet disintegrates into single drops which may bedeflected electrostatically, inter alia. An observation volume isunderstood to be a volume area of a specific height, in whichmeasurements or observations are made. Observation volumes may bearranged in a defined two-dimensional grid of a certain height. Amicrotiter plate is understood to be a plate containing several mutuallyinsulated cavities (wells) in rows and columns. Often, microtiter platesare rectangular and usually consist of plastic. An imager is understoodto be an imaging apparatus such as an automatic microscope which, e.g.,enables examining entire microtiter plates under a microscope. In thiscase, imagers are configured to individually photograph each well of themicrotiter plate in high resolution. Successively, this enables the userto find single cells in the wells.

As explained above, known systems lack the verification that a dispenseddrop comprising a cell or a particle has actually landed in the well ofa microtiter plate. For this purpose, a secondary technology such as animager has generally been used. Accordingly, the user later does notknow if the desired single cell has actually reached the well as long asshe/he is solely using the dispensing system.

Further, it was also realized that there are more problems in usingimagers. The area to be photographed by the imager is huge when comparedto a cell, by a factor of approximately 1:1,000,000. In order to ensurethat only one cell is in the well, the entire well area has to bescanned. At the same time, the resolution has to be high enough that thecell may be reliably identified as such. The higher the resolution, thesmaller the image field, the longer scanning takes. Further, scanningmay involve capturing several images in a spatially offset manner andcombining these to an overall image. If the cell is located exactlybetween two such images, cut-off or, in the worst case, disappearance ofthe illustration of the cell may occur due to combining. Furthermore,the optical focal depth is limited due to the high optical resolution.If the system is not precisely focused, cells are blurred and, in theworst case, may be overlooked. The scan of the entire well volume, i.e.,all focal planes from the bottom to the surface of the liquid, isexpensive with regard to time and data consumption and, thus, hardlyfeasible. Using current imager technology, it would take approximatelyten hours to scan a 96 well plate. The resulting data volume would beabout 40 GB. Based on the amount of plates and the time the data wouldhave to be stored, this would not be possible. Furthermore, the cellsare transported to the focal plane i.e., to the well bottom, before thescan. Typically, this is achieved by centrifugation after the celldeposition. For this purpose, the plates are centrifuged at highcentrifugal forces until the cells are located at the bottom. Due to theoccurrence of radial centrifugal forces during acceleration anddeceleration, cells may be transported to the outside. They then oftencome to rest in the corners of the wells. There, they are very difficultto identify. Microtiter plates are subject to manufacturing tolerancesdespite extensive standardization. The height of the well bottom mayvary both in the total and from well to well. This causes the level inwhich the cells lie and, thus, the focus to not be uniform. A wrongfocus may smear the objects towards the edge.

Due to the way the microtiter plates are produced by injection moldingor deep drawing, the wells usually comprise demolding edges and thecorners at the bottom are not 90° but slightly round. This results instrong diffraction and shading effects in the imager. Thus, cells whichcome to rest in the corners may possibly not be identified unambiguouslyor at all. If the well bottom becomes higher towards the edge, cells areonly in focus in the center and out of focus on the outside.Furthermore, single cells may be depicted twice due to refractioneffects. A so-called ghost image of the cell may arise in the immediatevicinity of the actual image. Thus, however, it cannot be reliablydetermined whether this is a ghost image or actually a second cell.

As described above, the microtiter plates are usually brought from adispensing system to an imager system in order to check if cells orparticles are arranged in the wells of the microtiter plates. By meansof the steps of centrifuging and changing the microtiter plates betweenapparatuses, as well as by means of the passing time between depositingthe cell by dispensing and sensing in the well, the cells in the wellmay practically come to rest anywhere at the bottom of the well. On theleft-hand side, FIG. 6 shows a fluid container 100 in which a cell 102has sunk to the bottom of the fluid container 100, e.g., the well of themicrotiter plate, by settling due to time passed. The illustration inthe middle of FIG. 6 shows a movement of the cell 102 on the bottom by atransport. The illustration on the right side of FIG. 6 shows a movementof the cell 102 by means of centrifugal forces as they may occur due tocentrifuging, for example. These observations show that the cells in thewell may practically come to rest anywhere on the bottom, while theyactually often come to rest in the corners.

Switching to other substrates comprising a smaller well bottom areawould theoretically solve some problems such as combining the images.However, this has other drawbacks. The ratio between a planar surface ofthe well bottom to the non-planar edge region, in which shading anddefocusing occur, would shift into the negative. The probability of acell coming to rest at the edge would increase. The area at the wellbottom or, above all, the volume of the well available to the cells forgrowing would be significantly smaller. Cells would grow worse and couldnot form sufficiently large populations. This would cause the entirework process to be more complex. Due to the small well volume, themedium would have to be exchanged or filled in order to supply the cellswith nutrients for a sufficiently long period of time. The risk ofcross-contamination or the probability of premature death of thepopulation would increase.

Thus, the inventors have realized that a dispensing technology alone isnot sufficient for the verification of a single cell in a fluidcontainer such as a well of a microtiter plate. Furthermore, due to theabove-described problems, imagers are also limited in their significancein this case. Ultimately, this may lead to the fact that the optimalpopulation selected for the production cannot reliably be identified asmonoclonal and, thus, has to be discarded. This leads to high economicrisks and high costs.

Embodiments of the invention provide apparatuses and methods solving theabove-described problems and enabling a reliable detection even ofsingle cells or particles in a fluid container.

In FIG. 1, an embodiment of an apparatus for detecting cells orparticles is shown. The apparatus includes a fluid container 10. Forexample, the fluid container may be a well (cavity) of a microtiterplate comprising an array of corresponding wells. The fluid containermay comprise a bottom and side walls limiting a volume of the fluidcontainer and enabling the fluid container to be at least partiallyfillable with a fluid. In embodiments, the fluid container 10 consistsof a transparent material. The fluid container 10 is at least partiallyfilled with a fluid 12 such as a liquid. For example, the liquid may bea nutrient solution for a cell culture. In the following, reference ismade to a liquid 12. The apparatus further comprises a dispenser 14configured to dispense at least one cell or particle 16 into a definedsub-volume 18 of the liquid 12. The dispenser 14 may be a drop-on-demanddispenser configured to dispense a single drop, in which a cell or aparticle is encapsulated, from a nozzle 22. The dispenser 14 ispositioned or may be positioned relative to the fluid container 10 suchthat the cell or the particle is dispensed into the defined sub-volume18. Accordingly, the dispenser may be configured to dispense singledrops from a cell suspension or particle suspension, and may comprise astructure as described in WO 2011/154042 A1, for example.

The apparatus further comprises a detection apparatus 22 configured to,in a time-coordinated manner with dispensing the at least one cell 16(or the at least one particle) by the dispenser 14, perform a detectionin the defined sub-volume 18 and/or in one or several sub-volumesunderneath the defined sub-volume in order to sense the at least onecell 16 when entering the fluid 12 or immediately after entering thefluid 12.

In examples, the fluid container is part of the apparatus. In examples,the fluid container is not part of the apparatus and may be providedseparately from the apparatus.

With regard to the explanation of the defined sub-volume and the one orseveral sub-volumes arranged underneath the defined sub-volume,reference is made to FIG. 3, which shows a schematic perspective view ofthe fluid container 10. In FIG. 3, the sub-volumes are illustrated asslices, the defined sub-volume 18 being formed by the uppermost slice.For example, the defined sub-volume 18 may extend downwards by apredetermined depth from the liquid surface of the liquid arranged inthe fluid container 10. The depth of each sub-volume may correspond tothe depth of focus of a focal plane of the detection apparatus. Forexample, the same may be in the range of 40 μm to 60 μm. In theillustration in FIG. 3, for reasons of simplification, it is assumedthat the liquid completely fills the container 10. In reality, thecontainer will usually only be partially filled with the liquid. As canbe seen in FIG. 3, the area A1 of the defined sub-volume 18 issignificantly smaller than the area A2 of the fluid container 10. Here,area is understood to be the area parallel to the liquid surface. Theone or several sub-volumes underneath the defined sub-volume 18 arearranged underneath the sub-volume 18 with increasing depth. Thesub-volumes may overlap in a direction perpendicular to the liquidsurface. The sub-volumes 18 and 18 a-18 d may each be configured suchthat a detection by the detection apparatus 22 may occur in the entiresub-volume. For example, the sub-volumes are dimensioned such that animaging sensor may generate a focused image of the respectivesub-volume.

The dispenser 14 and the detection apparatus 22 may be connected with acontrol 24 which coordinates dispensing the cell or the particle by thedispenser and detecting by the detection apparatus 22 in a timelymanner. In embodiments, the control may be arranged in the dispenser orthe detection apparatus. As is obvious to those skilled in the art, thecontrol may be implemented by, e.g., an accordingly programmed computingmeans or by a user specific integrated circuit. In embodiments, thedetection apparatus may be configured to sense the at least one cell orthe at least one particle no later than ten seconds after entering thefluid, i.e., the fluid 12 in the embodiment shown. For example, thedetection apparatus may be configured to perform detection in one of thesub-volumes when it is expected that the cell or the particle is locatedin the sub-volume. If the detection occurs in the sub-volume 18 arrangeddirectly below the surface of the liquid 12, sensing may occurimmediately after dispensing by the dispenser, e.g., in one second or inan even shorter period of time. In embodiments of the invention, thedetection apparatus is configured to sense the cell or the particle in asub-volume arranged above the bottom of the fluid container. Thus, theobject may be sensed before it has reached the bottom of the fluidcontainer.

FIG. 2 shows an embodiment of an apparatus for detecting cells orparticles, wherein the detection apparatus comprises an optical sensor32. A dispenser (not shown in FIG. 2) is configured for dispensing drops34 of a cell suspension, a cell 16 being arranged in the drop 34. Thedispenser dispenses the drop into the fluid container 10, e.g., in theform of a well of a microtiter plate, which is prefilled with a cellmedium 12. In embodiments, the shape of the fluid container may beselected such that the surface of the fluid is flat. An optical sensor32 such as a microscope comprising an adjustable focus is located belowthe transparent fluid container 10. A cell/a particle is alreadycaptured with the optical sensor when entering the fluid in the fluidcontainer 10. The optical sensor comprises a camera and optics. Theoptical sensor 32 focuses on the system through the transparent fluidcontainer. For this, the optical sensor 32 representing an imagecapturing apparatus focuses on a defined sub-volume directly underneaththe surface of the liquid 12. For example, the optical sensor 32 mayfocus on a sub-volume directly underneath the liquid surface or on asub-volume in a depth of less than 5 mm from the surface of the liquid12. The aim is to verify that the cell/the particle actually lands inthe reservoir. It is not necessary to wait until the cell/the particlehas sunk to the bottom of the reservoir. In the described sensing, it isnot important where on the bottom of the fluid container the cell/theparticle finally comes to rest.

In embodiments, single drops of a cell suspension or a particlesuspension each comprising a volume of approximately 200 pl may bedispensed into a well of a microtiter plate. For example, the well maybe filled up to half with a liquid beforehand, while the focus of theoptical sensor may be constantly held underneath the liquid surface.Thus, the cell/the particle may settle through the focal plane of theoptical sensor 32, which may be a light microscope. Capturing an imagein a time-coordinated manner with dispensing the cell/the particleallows for a reliable detection of the cell/the particle in the fluidcontainer. Furthermore, in embodiments, an image series of the definedsub-volume (or several defined sub-volumes) may be captured in order toallow for an even more reliable detection of the cell/the particle.Practical experiments have shown that by using such a structure it iseasily possible to recognize that the object (the cell/the particle) inthe observation volume (the defined sub-volume) penetrates the liquidand, successively, settles towards the bottom, wherein the same may beobserved by the optical sensor.

In alternative embodiments, the focal plane of the optical sensor may bemoved against the settling movement of the object in order to reduce thetime until detection. In other words, the detection apparatus may beconfigured to, starting with a sub-volume in a greater depth,successively perform detections in several sub-volumes of a respectivelydecreasing depth.

Performing several detections, e.g., by an image capturing apparatus,enables that the object is exactly in focus during performing the atleast one detection and, thus, may be absolutely reliably detected.Practical experiments have shown that, e.g., a polystyrene particlecomprising a diameter of 15 μm may be easily sensed by means of acorresponding procedure.

For example, several sub-volumes comprising a respectively decreasingdepth are shown in FIG. 3 of the present application and are providedwith the reference numerals 18 a-18 d. For example, a detection couldimmediately be started in the sub-volume 18 d after dispensing the dropby the dispenser and detections could be successively performed insub-volumes comprising a respectively decreasing depth, i.e., from 18 cto 18 b to 18 a to 18. Due to this, it is possible to sense with a highreliability a cell or a particle brought into the liquid 12 in the fluidcontainer 10.

In alternative embodiments, the detection apparatus could also beconfigured to, starting with a sub-volume in a lesser depth,successively perform detections in several sub-volumes comprising arespectively increasing depth.

In embodiments of the invention, the defined sub-volume may comprise anarea of less than 10 mm². For example, the sub-volume may comprise anarea of 2×2 mm at a depth corresponding to the depth of focus of a focalplane of the detection apparatus. In embodiments, the detectionapparatus may be configured to capture an image sequence in a sub-volumeuntil the cell or the particle settles into the sub-volume. Inembodiments, the detection apparatus may be configured to focus on asub-volume arranged directly underneath the liquid surface, or on asub-volume arranged in a depth of less than 5 mm below the liquidsurface. In embodiments of the invention, the detection apparatus may beconfigured to perform several detections of the respective sub-volume,e.g., with a capturing rate between 50 Hz and 150 Hz, e.g., 100 Hz. Inembodiments, the detection apparatus may be an image capturing apparatuswith an image capturing rate of 100 Hz. In embodiments, the focus of theimage capturing apparatus may be traversed in order to perform avertical scan in a limited lateral region. In embodiments, for example,a traverse speed may be 5 mm/s while images are captured in order tocapture images at different depths. In embodiments, for example, thevolume of the liquid in the fluid container may be 150 μl, which is atypical volume in a cell culture.

Embodiments may be used in dispensing a documented number of particles.In particular, embodiments of the invention may be used in a cell lineproduction in order to dispense single cells into cavities of amicrotiter plate in a reliable and documented manner. In embodiments ofthe invention, single cells or a particular number of cells may beprinted in monoclonal cell cultures to verify the monoclonality and forfurther processing. In particular, embodiments may be used for singlecell analysis.

Hence, embodiments of the invention provide a method in which an object,i.e., a cell or a particle, is dispensed into a defined sub-volume of afluid with which a fluid container is at least partially filled, step 50in FIG. 4. The object is sensed when entering the fluid or immediatelyafter entering the fluid. For this, one or several detections may beperformed in the defined sub-volume and/or in one or several sub-volumesunderneath the defined sub-volume in a time-coordinated manner withdispensing the at least one cell or the at least one particle, step 52in FIG. 4. Sensing the object may occur no later than ten seconds afterentering the fluid, advantageously, no later than five seconds and moreadvantageously, no later than one second after entering the fluid. Inembodiments, the defined sub-volume comprises an area which is smallerthan the area of an entry opening of the fluid container. Inembodiments, the object is dispensed onto a surface of the fluid. Inembodiments, the object is dispensed into a defined fluid volumeunderneath the surface of the liquid.

In embodiments, the dispenser is configured to transfer particlesuspension or cell suspension selectively into the fluid container at apredefined position. Possible mechanisms for this are: drop-on-demandprinting (in a piezoelectric or thermally driven manner), afluorescence-based flow symmetry (FACS—fluorescence activated cellsorting), pipetting (manually or by means of a pipetting robot), adosing apparatus (valve-based, by means of a displacer, by means of asyringe pump, etc.) or a micro-manipulator. In embodiments, thedetection apparatus is configured to focus on the upper edge of theliquid level in the center of the fluid container (reservoir). Withthis, the region of the impact of the drop, i.e., of the transportvolume comprising the object therein, may automatically be in focus.Alternatively, as described above, the liquid volume in the center ofthe fluid container may be focused through starting from below as soonas the drop has been dispensed by the dispenser. This ensures that theobject is in focus at a random point in time. For this purpose, it isnot necessary to know the exact filling level of the fluid container inorder to find the focus.

In order to keep the meniscus of the liquid in the reservoir as flat aspossible and to, thus, have a reproducible liquid level in the fluidcontainer, reservoirs comprising special shapes may be used, e.g., asdescribed in EP 1 880 764 B1. For example, flat steps are excellentlysuitable for drawing the meniscus flat when the fluid container isfilled with a precisely known liquid volume.

In embodiments of the invention, the object may be applied to thesurface of a fluid in the fluid container or be inserted underneath thesurface into the fluid. In embodiments, the detection occurs by means ofan image capturing apparatus focusing on a corresponding sub-volume. Inalternative embodiments, different detection apparatuses may be used.For example, a detection apparatus may be implemented by electrodesformed in the wall of the fluid container, which are configured to sensea capacity between the same. For example, several such electrodes may bearranged in different depths of the fluid container in order to performdetection in several different depths.

Hence, embodiments of the invention provide apparatuses and methods inwhich an observation volume smaller than the container volume isobserved in the fluid container (reservoir). In embodiments, solely theentry point of the object into the fluid or the liquid is observed.Accordingly, a sensor for observing the observation volume and amechanism for selectively dispensing particles solely into theobservation volume may be provided. Accordingly, apparatuses and methodsfor recognizing particles and cells in a liquid comprise a reservoir ora cavity for receiving liquids, a mechanism for transferring liquidswith one or several cells/particles and a sensor for recognizing singleor several particles or cells. In embodiments, the reservoir is areservoir for receiving particle suspensions or cell suspensions, themechanism is a mechanism for selectively transferring the particlesuspension or cell suspension into the reservoir at a predefinedposition, and the sensor is a sensor for recognizing single or severalparticles or cells in a cell medium at the predefined position.

According to embodiments, the sensor may be an optical sensor or animaging sensor. The imaging sensor may comprise an adjustable focus andmay be configured to focus through the observation volume. In otherwords, the imaging sensor may be configured to vertically scan theobservation volume. In embodiments, this occurs from underneath thefluid container so that an adjustment of the focus occurs in a depthdirection. In embodiments, transferring a particle suspension or cellsuspension into the fluid in the fluid container occurs without contactin the form of free-flying drops. In embodiments, the free-flying dropcomprises a volume of a maximum of 100 nl. In embodiments, the fluidcontainer is prefilled with a liquid. In embodiments, the liquid withthe cell/the particle is inserted into the fluid container. Inembodiments, the fluid container is configured such that a liquidlocated therein comprises a flat surface (meniscus). In embodiments, forthis, the fluid container comprises an edge of a particular depth, thevolume of the liquid in the fluid container being adapted such that theliquid reaches up to the edge. In embodiments, the fluid containercomprises a volume of at least 100 μl.

In embodiments, a mechanism is provided by which the fluid container,the dispenser and the detection apparatus may be traversed towards eachother in order to subsequently insert cells/particles into several fluidcontainers, e.g., into the wells of a microtiter plate. For example,such a mechanism may be configured to move the several fluid containers,e.g., the microtiter plate, relative to the dispenser and the detectionapparatus or to move the dispenser and the detection apparatus relativeto the several fluid containers. Thus, it is possible to subsequentlyinsert cells/particles into several fluid containers and immediatelyreliably sense if a cell/particle has ended up in each of the fluidcontainers.

The technique described herein provides significant advantages overknown methods.

A significant drawback of known dispensing technologies in combinationwith imagers is the time and the process steps between dispensing, i.e.,the cell transport into the fluid container (the well), and imaging thewell. Here, a single cell was first deposited in a well of themicrotiter plate, the microtiter plate was then removed from thedispenser, the plate was then centrifuged, the plate was then insertedinto an imager and sensing by the imager then occurred. In addition,there are also the bad conditions in imaging the well bottom due to themanufacturing-related geometries of the wells. These drawbacks arecompensated by the technique described herein. Sensing occurs directlywith depositing the cell, i.e., dispensing. Depositing may be performedin a highly precise manner so that the cell reaches the well at apredefined position, e.g., centrally, and the same may already bescanned directly at the entry point of the liquid in the well. By this,the plate does not have to be moved and/or the cells do need not becentrifuged to the well bottom. By this, the steps of removing the platefrom the dispenser, centrifuging the plate and inserting the plate intothe imager may be omitted. Furthermore, sensing (scanning) may solelyoccur from the bottom up using a focus shift at the location of entry ofthe cell into the fluid container (the well). This may occur veryquickly and the cell may automatically be in the image.

Therefore, embodiments of the present invention are advantageous in thatdispensing and detecting occur directly in succession and moving theplate and therefore moving the cell in the container in anuncontrollable manner do not occur. There are no intermediate stepsbetween dispensing and detecting. Furthermore, sensing occurs in thefree liquid and not at the well bottom. Therefore, there are no shadingeffects or refraction effects and no ghost images of cells. Furthermore,other drawbacks may be avoided which may impair sensing at the wellbottom, e.g., scratches, finger prints (bottom/outside),(electrostatically) attracted dust (bottom/outside) or dirt (debris)from above/inside, which, e.g., was centrifuged to the well bottom withthe cell. In embodiments of the invention, vertical scanning is usedinstead of horizontal scanning so that focus problems and a necessity tocombine images do not exist. The volume to be scanned is substantiallysmaller than the entire well volume. In contrast to horizontal scanning,traversing the plate is omitted, which in turn allows for fastersensing. Finally, the image quality does not anymore depend on thequality of the fluid container, e.g., the microtiter plate substrates ortheir bottoms, since sensing occurs while the cell/the particle islocated in the free liquid.

FIG. 5 illustrates a comparison of an embodiment described herein with aknown method, the time axis being plotted from top to bottom. In eachcase, a cell suspension is used as the base material. In the methoddescribed herein, the cell suspension is transferred into reservoirs ata predefined position, step 60. Simultaneously, direct examination undera microscope of the predefined position occurs, step 62. As a result ofsteps 60 and 62, information about the cell count per reservoir isprovided.

In contrast, in known methods, the cell suspension is transferred intoreservoirs, step 70, the reservoirs are centrifuged, step 72, andexamining the entire bottom of the reservoir under a microscope occurs,step 74. Thus, known methods comprise a significantly higher timeexpenditure, the height of the single process blocks in FIG. 5 beingcorrelated with the duration of the corresponding steps. It has beenfound that a simplification and acceleration of the overall process isachieved by the methods described herein.

Hence, embodiments of the present invention enable an improvedverification of single cells in a cell separation, while the entireprocess is simplified and accelerated. Simultaneously, the prerequisiteremains that the cell may be dispensed into a sufficiently large volumeenabling a subsequent cultivation (growth of the cells). Embodimentsinclude a corresponding step of a cell cultivation in the fluidcontainer after detecting a cell in the same.

While this invention has been described in terms of several embodiments,there are alterations, permutations, and equivalents which fall withinthe scope of this invention. It should also be noted that there are manyalternative ways of implementing the methods and compositions of thepresent invention. It is therefore intended that the following appendedclaims be interpreted as including all such alterations, permutationsand equivalents as fall within the true spirit and scope of the presentinvention.

The invention claimed is:
 1. A method for detecting cells or particlesin a fluid container, comprising: dispensing at least one cell or atleast one particle into a defined sub-volume of a fluid, wherein thefluid at least partially fills a fluid container, and wherein thedefined sub-volume is directly underneath a surface of the fluid andextends downward by a predetermined depth from the surface of the fluidwith which the fluid container is at least partially filled; performing,in a time-coordinated manner with dispensing the at least one cell orthe at least one particle, a detection in the defined sub-volume and/orin one or several sub-volumes underneath the defined sub-volume in orderto sense the at least one cell or the at least one particle whenentering the fluid or no later than 10 seconds after entering the fluid.2. The method according to claim 1, wherein the fluid is a liquid andthe defined sub-volume comprises an area parallel to a liquid surface ofthe liquid in the fluid container, which is smaller than the area of anentry opening of the fluid container.
 3. The method according to claim1, wherein the at least one cell or the at least one particle isdispensed onto a surface of the fluid.
 4. The method according to claim3, wherein a detection of the at least one cell or the at least oneparticle is performed in the defined sub-volume comprising a depth ofless than 5 mm from the upper surface of the fluid.
 5. The methodaccording to claim 1, wherein, starting with a sub-volume in a firstdepth, detections are successively performed in several sub-volumescomprising a respectively decreasing depth, or, starting with asub-volume in a second depth, detections are successively performed inseveral sub-volumes comprising a respectively increasing depth.
 6. Themethod according to claim 1, wherein performing a detection comprisesfocusing on the defined sub-volume and/or the one or several sub-volumesunderneath the defined sub-volume and capturing images of the definedsub-volume and/or of the one or several sub-volumes underneath thedefined sub-volume.
 7. The method according to claim 6, wherein thefluid container is transparent and performing a detection occurs bymeans of an image capturing apparatus arranged underneath the fluidcontainer.
 8. The method according to claim 1, comprising positioning adispenser, a detection apparatus and each one of several fluidcontainers relative to each other in order to sense the at least onecell or the at least one particle when entering the fluid or immediatelyafter entering the fluid of each one of the several fluid containers.